James Cameron speaks at the Avatar question-and-answer session during the Comic-Con convention in San Diego. (John Shearer/Getty Images)

Director James Cameron premiered footage of his highly anticipated film Avatar Thursday at Comic-Con in San Diego.

More than 6,000 fans at the convention got to see a 25-minute sneak peek of the 3-D adventure, Cameron's first film since the 1997 blockbuster Titanic.

Cameron, who once served as chief executive of the special effects firm Digital Domain, wrote the film's story 14 years ago.

"I decided to write a story that was full of creatures and characters that would push the art of CG for that company," Cameron said.

Digital Domain, unfortunately, did not have the technology to create Cameron's vision, so the Canadian director had no choice but to put his project on hold. Ten years later, with technology advanced, Cameron decided to take a stab at the film.

"[It was about] wanting to do something that has a conscience, that maybe in the enjoying of it makes you think a little bit about the way you interact with nature and your fellow man," said Cameron before premiering the footage.

Avatar is set in a fictional planet called Pandora. Green forests, pink flowers, strange dinosaur creatures and the Navi people inhabit the planet. In the movie, the people of Earth find themselves at odds with the Navi people.

Sam Worthington stars as Jake Sully, a solider on duty in Pandora, and Zoe Saldana stars as Neytin, the Navi princess.

The film also stars Sigourney Weaver as Dr. Grace Augustine.

Fans can see a free 15-minute preview of Avatar in digital theatres worldwide on Avatar Day, Aug. 21.

Avatar is set to hit theatres Dec. 18.

With files from The Associated Press